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The webpage How to use TeamViewer should only open when finishing an installation of the program.
Could you please uninstall the version you have right now and install the latest version here:
and see if this behaviour occurs after a reboot of the computer?
I uninstalled and then reinstalled TeamViewer. Upon finishing the install, the "How to Use TeamViewer" page did not open. I then rebooted and Firefox started of its own accord and the How to Use TeamViewer page was open. I then closed this page, closed Firefox, and rebooted again. The How to Use TeamViwere page was open again.
Please provide more troubleshooting steps.